Preservation of ether



March 1952 E. MALLINCKRODT, JR., ETAL 2,587,744

PRESERVATION OF ETHER Filed Feb. 12. 1949 Patented Mar. 4, 1952 UNITEDSTATES ATENT OFFICE PRESERVATION F ETHER Application'February 12, 1949,.Serial No; 76,142

'7 Claiins. 1 V

This invention relates to the preservation'of ether and moreparticularly to improved means for packaging ether.

Among the objects of the present invention are the provision ofimproved'means for protecting packaged ether against decomposition; theprovision of means of the character described-which do not causecorrosion of the container; th'eprovision of an improved container forpackaging ether; and, the provision of a process for manufacturingimproved ether containers. Other objects will be in part apparent and inpart pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, steps and sequence of steps, features of construction andmanipulation, and arrangements of parts which will be exemplified in thestructures and methods hereinafter described, and the scope oftheapplication of which will be indicated in the following claims.

In the accompanying drawing, in which one of various possibleembodiments of the invention is illustrated,

Fig. 1 is a vertical section through an ether can showing one form ofour invention; and,

Fig. 2 is a section taken along the line 22 on Fig. 1 but on an enlargedscale.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawing.

Because diethyl ether is a highly volatile and inflammable liquid whichis hazardous to ship and to store, it is usually packaged in containersmade of tin plate in preference to containers made of glass or otherfragile materials. From the standpoint of safety, durability, and lowcost, tin cans have been entirely satisfactory as containers for etherand their use has been widespread for many years. They are, however,subject to one serious disadvantage. Conventional bright tin-plategreatly increases the tendency for ether to be oxidized by air in thecontainer. Aldehydes and peroxides which may be formed by such oxidationare particularly objectionable in anesthetic ether, as evidenced bytheir limitation to merest traces by the U. S. Pharmacopoeia.

It has been customary to overcome this disadvantage to a considerableextent by covering the inner surface of the container with either anadherent layer of tin oxide or with a coating of metallic copper. Theadherent layer of tin oxide is usually produced by heating the cans atan elevated temperature. The treatment is simple, but it has been foundthat the protection which it aifordsthe ether is somewhat variable.Copper plating the can, on the other hand, is more complicated and alsohas the disadvantage that it is difficult to apply a copper coating tothe tin surface without increasing the tendency of the container tocorrode. Other methods have also been proposed, for example, to packagethe ether in contact with reducing substances, such as cuprous oxide oriron, but these methods have found little favor.

The improved ether container of the present invention comprises a canmade of conventional tin-plate; especially treated to produce anadherent coating of cupric and tin oxides on the inner surface.Containers of this type have been found to possess definite advantages.The coating is easily and inexpensively applied using simple, readilyavailable equipment, and provides reliable protection. It is visible onthe surface of the tin as a semi-transparent brown stain which ispractically insoluble in ether and is not dislodged by agitation ofether in the container.

Referring now to the drawing, an ether can I having conventional sidewalls 3', bottom 5 and top! is'shown. An opening 9 in top 7 receivesneck H which is of a type to receive a vaportight closure member l3.

The interior of container I is coated as shown at' I5 (see Fig. 2) withan adherent coating of cupric and tin oxides. The relative thickness'ofthe coating has been exaggerated in the drawing to show its location.

The protective coating is preferably produced by wetting the interior ofthe container with a solution of a thermally unstable copper compound,then drying the surface of the container bydirecting a stream of warmair against it, and finally heating the container in the presence of airata temperature and for a time sufficient to convert'substantially allof the copper to a divalent oxide and simultaneously to form a surfacelayer of tin oxide. Part or all of these oxides may be in'the form of adouble oxide of copper and tin, but for the purposes of this inventionthe exact composition need not be known. What is important is that theoxide layer is adherent and affords reliable protection to the ether.

Examples of thermally unstable copper compounds of the type which can beused with this invention are copper acetate, copper formate, and copperacetylacetonate. Numerous solvents for the preferred copper compoundsare known, but the adherence of the oxide coating formed by theprocesses of this inventionis to a large degree dependent upon thenature of the solvent employed.

We have found that the use of amines or mixtures of amines as solventsleads to the most strongly adherent coating. For reasons of economy weprefer to dilute the amine solutions of the copper salts with a low costsolvent, for example, isopropyl alcohol. A mixture of equal parts byvolume of diethylamine and di-isopropylamine is particularly desirableas this mixture evaporates at substantially the same rate as isopropylalcohol. The concentration of the copper salts in the solution need beonly a few tenths of a per cent for maximum protection. The exactpercentage is not critical, but no advantage is derived from using agreater percentage and there is the danger that as the oxide coatingbecomes thicker it may also become weaker and break away from thesurface of the can, thereby producin a residue in the ether. Manysolvents may be used as diluents for the amine solution in place ofisopropyl alcohol. Among them are ether, the lower aliphatic alcohols,ethyl acetate, petroleum ether, and toluene.

Example A number of tin cans, of the type commonly employed forpackaging ether, were treated in the following manner. A stock solutionwas prepared by dissolving 15 pounds of cupric acetate in a mixture ofgallons of di-isopropylamine and 10 gallons of diethylamine. To 1 gallonof this solution, sufiicient isopropyl alcohol was added to make a totalvolume of 38 gallons. Some of the resulting solution was poured intoeach of the cans to be treated, the cans were turned and rotated so thatthe inner surface was entirely wetted with the solution, and the excesssolution was then poured out. The cans were dried with a stream of hotair, then baked at a temperature of about 155-160 C. for 36 hours. Thecontainers were filled with anesthetic grade ether, sealed in thecustomary manner, and then stored at a temperature of 90 F.Periodically, cans were selected at random and the contents were testedfor the presence of aldehydes and peroxides.

After thirteen months the ether met all the requirements of the tests ofthe U. S. Pharmacopoeia. Moreover, when tested by still more sensitivemethods no trace of aldehydes or peroxides was found. In controlexperiments conducted in parallel, ether stored in untreated butotherwise identical containers failed badly in the limiting tests of theU. S. Pharmacopoeia for aldehydes and peroxides within three months, andether stored in containers which had been given a coating of tin oxideonly showed traces of aldehydes within six months and failed to meet theminimum U. S. P. requirements within thirteen months.

Attention is directed to our copending application, Serial No. 209,396,filed February 5, 1951.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

We claim:

1. A container for ether comprising a container member and a coating onthe interior of said container member, said coating comprising cupricoxide and a tin oxide.

2. A container for ether comprising a container member and a coating onthe interior of said container member, said coating comprising cupricoxide and a tin oxide, said oxides being in intimate admixture.

3. A container for ether comprising a container member and a coating onthe interior of said container member, said coating comprising cupricoxide and a tin oxide, said oxides being in intimate admixture andfirmly adhering to the interior of the container member.

4. A container for ether comprising a metallic container member,interior surfaces of said container member being tin, said containermember having on its internal surfaces a firmly adherent coating ofcupric oxide and tin oxide in intimate admixture to form a preservativecoating to preserve ether stored in said container member.

5. The method of preventing the deterioration of other which comprisesstoring ether in a container in the presence of a tin oxide and cupricoxide.

6. The method of preventing the deterioration of ether which comprisesstoring ether in a container having an interior surface coatingincluding a tin oxide and cupric oxide.

7. The method of preventing the deterioration of ether which comprisesstoring ether in a container having an interior surface coating of a tinoxide and cupric oxide firmly adhered to a layer of tin.

' EDWARD MALLINCKRODT, JR.

ARCHIE E. RUEHLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,632,309 Nitardy June 14, 19272,105,906 Demers Jan. 18, 1938 2,135,886 Elder Nov. 8, 1938 2,237,259Marland Apr. 1, 1941 2,245,561 Nelson et a1 June 1'7, 1941 2,272,609Kennedy et al Feb. 10, 1942 2,315,475 Cobb et al Mar. 30, 1943 2,316,804Musher Apr. 20, 1943

1. A CONTAINER FOR ETHER COMPRISING A CONTAINER MEMBER AND A COATING ONTHE INTERIOR OF SAID CONTAINER MEMBER, SAID COATING COMPRISING CUPRICOXIDE AND A TIN OXIDE.